The observation of Higgs pair production at high-energy colliders can give evidence for the presence of a triple Higgs coupling. However, the actual determination of the value of this coupling is more difficult. In the context of general models for new physics, double Higgs production processes can receive contributions from many possible beyond-Standard-Model effects. This dependence must be understood if one is to make a definite statement about the deviation of the Higgs field potential from the Standard Model. In this paper, we study the extraction of the triple Higgs coupling from the process $e^{+}{e}^{-}\to Zhh$. We show that, by combining the measurement of this process with other measurements available at a 500 GeV $e^{+}{e}^{-}$ collider, it is possible to quote model-independent limits on the effective field theory parameter $c_6$ that parametrizes modifications of the Higgs potential. We present precise error estimates based on the anticipated International Linear Collider physics program, studied with full simulation. Our analysis also gives new insight into the model-independent extraction of the Higgs boson coupling constants and total width from $e^{+}{e}^{-}$ data.

Future $e^{+}{e}^{-}$ colliders give the promise of model-independent determinations of the couplings of the Higgs boson. In this paper, we present an improved formalism for extracting Higgs boson couplings from $e^{+}{e}^{-}$ data, based on the effective field theory description of corrections to the Standard Model. We apply this formalism to give projections of Higgs coupling accuracies for stages of the International Linear Collider and for other proposed $e^{+}{e}^{-}$ colliders.

We model spherically symmetric black holes within the group field theory formalism for quantum gravity via generalized condensate states, involving sums over arbitrarily refined graphs (dual to three-dimensional triangulations). The construction relies heavily on both the combinatorial tools of random tensor models and the quantum geometric data of loop quantum gravity, both part of the group field theory formalism. Armed with the detailed microscopic structure, we compute the entropy associated with the black hole horizon, which turns out to be equivalently the Boltzmann entropy of its microscopic degrees of freedom and the entanglement entropy between the inside and outside regions. We recover the area law under very general conditions, as well as the Bekenstein-Hawking formula. The result is also shown to be generically independent of any specific value of the Immirzi parameter.

We construct an analytic solution for a one-parameter family of holographic superconductors in asymptotically Lifshitz spacetimes. We utilize this solution to explore various properties of the systems such as (1) the superfluid phase background and the grand canonical potential, (2) the order parameter response function or the susceptibility, (3) the London equation, and (4) the background with a superfluid flow or a magnetic field. From these results, we identify the dual Ginzburg-Landau theory including numerical coefficients. Also, the dynamic critical exponent $z_{\mathrm{D}}$ associated with the critical point is given by $z_{\mathrm{D}}=2$ irrespective of the value of the Lifshitz exponent $z$.

We show how the Weyl anomaly generated by gauge fields, can be computed from manifestly gauge invariant and diffeomorphism invariant exact renormalization group equations, without having to fix the gauge at any stage. Regularization is provided by covariant higher derivatives and by embedding the Maxwell field into a spontaneously broken $U(1|1)$ supergauge theory. We first provide a realization that leaves behind two versions of the original $U(1)$ gauge field, and then construct a manifestly $U(1|1)$ supergauge invariant flow equation which leaves behind only the original Maxwell field in the spontaneously broken regime.

We construct static and also time-dependent solutions in a nonlinear sigma model with target space being the flag manifold $F_2=SU(3)/U(1{)}^2$ on the four-dimensional Minkowski spacetime by analytically solving the second-order Euler-Lagrange equation. We show that the static solutions saturate an energy lower bound and can be derived from coupled first-order equations though they are saddle-point solutions. We also discuss basic properties of the time-dependent solutions.

The shadow of a black hole can be one of the strong observational evidences for stationary black holes. If we see shadows at the center of galaxies, we would say whether the observed compact objects are black holes. In this paper, we consider a formula for the contour of a shadow in an asymptotically-flat, stationary, and axisymmetric black hole spacetime. We show that the formula is useful for obtaining the contour of the shadow of several black holes such as the Kerr-Newman black hole and rotating regular black holes. Using the formula, we can obtain new examples of the contour of the shadow of rotating black holes if assumptions are satisfied.

We consider a model where particles are described as localized concentrations of energy, with fixed rest mass and structure, which are not significantly affected by their self-induced gravitational field. We show that the volume average of the on-shell matter Lagrangian ${\mathcal{L}}_m$ describing such particles, in the proper frame, is equal to the volume average of the trace $T$ of the energy-momentum tensor in the same frame, independently of the particle’s structure and constitution. Since both ${\mathcal{L}}_m$ and $T$ are scalars, and thus independent of the reference frame, this result is also applicable to collections of moving particles and, in particular, to those which can be described by a perfect fluid. Our results are expected to be particularly relevant in the case of modified theories of gravity with nonminimal coupling to matter where the matter Lagrangian appears explicitly in the equations of motion of the gravitational and matter fields, such as $f(R,{\mathcal{L}}_m)$ and $f(R,T)$ gravity. In particular, they indicate that, in this context, $f(R,{\mathcal{L}}_m)$ theories may be regarded as a subclass of $f(R,T)$ gravity.

In this paper we show that the on-shell Lagrangian of a perfect fluid depends on microscopic properties of the fluid, giving specific examples of perfect fluids with different on-shell Lagrangians but with the same energy-momentum tensor. We demonstrate that if the fluid is constituted by localized concentrations of energy with fixed rest mass and structure (solitons) then the average on-shell Lagrangian of a perfect fluid is given by ${\mathcal{L}}_m=T$, where $T$ is the trace of the energy-momentum tensor. We show that our results have profound implications for theories of gravity where the matter Lagrangian appears explicitly in the equations of motion of the gravitational and matter fields, potentially leading to observable deviations from a nearly perfect cosmic microwave background black body spectrum: $n$-type spectral distortions, affecting the normalization of the spectral energy density. Finally, we put stringent constraints on $f(R,{\mathcal{L}}_m)$ theories of gravity using the COBE-FIRAS measurement of the spectral radiance of the cosmic microwave background.

We consider a rapidly spinning black hole surrounded by an equatorial, geometrically thin, slowly accreting disk that is stationary and axisymmetric. We analytically compute the broadening of electromagnetic line emissions from the innermost part of the disk, which resides in the near-horizon region. The result is independent of the disk’s surface emissivity and therefore universal. This is an example of critical behavior in astronomy that is potentially observable by current or future telescopes.

We study disformal transformations of cosmological perturbations by vector fields in theories invariant under $U(1)$ gauge transformations. Three types of vector disformal transformations are considered: (i) disformal transformations by a single timelike vector; (ii) disformal transformations by a single spacelike vector; and (iii) disformal transformations by three spacelike vectors. We show that transformations of type (i) do not change either curvature perturbation or gravitational waves; that those of type (ii) do not change curvature perturbation but change gravitational waves; and that those of type (iii) change both curvature perturbation and gravitational waves. Therefore, coupling matter fields to the metric after disformal transformations of type (ii) or (iii) in principle have observable consequences. While the recent multi-messenger observation of binary neutron stars has singled out a proper disformal frame at the present epoch with a high precision, the result of the present paper may thus help distinguishing disformal frames in the early universe.

In this paper we first discuss how a Noether current corresponding to a gauge or a global symmetry can locally be introduced in a path integral irrespective of the boundary conditions defining the theory. We then consider quantization of gravity plus minimally coupled scalar field system in the phase space path integral approach. The complete gauge fixed action including the Faddeev-Popov determinant is obtained in the so called $\zeta$-gauge. It turns out that in this formalism while the dilatation survives as the residual symmetry of the gauge fixed action, other diffeomorphisms which require field dependent corrections fail to be so. The full Noether current for the dilatation is determined and the spatial boundary conditions that yield a finite and conserved charge are determined. The charge is shown to be expressible as a surface integral at infinity and the corresponding Ward identity gives the standard consistency relation of cosmological perturbations.

One of the major goals of future cosmic microwave background (CMB) measurements is the accurate determination of the effective number of neutrinos $N_{\mathrm{eff}}$. Reaching an experimental sensitivity of $\mathrm{\Delta }{N}_{\mathrm{eff}}=0.013$ could indeed falsify the presence of any nonstandard relativistic particles at 95% C.L. In this paper, we test how this future constraint can be affected by the removal of two common assumptions: a negligible running of the inflationary spectral index $n_{\mathrm{run}}$ and a precise determination of the neutron lifetime ${\tau }_n$. We first show that the constraints on $N_{\mathrm{eff}}$ could be significantly biased by the unaccounted presence of a running of the spectral index. Considering the Stage-IV experiment, a negative running of $\mathrm{d}n/\mathrm{d}\ln k=-0.002$ could mimic a positive variation of $\mathrm{\Delta }{N}_{\mathrm{eff}}=0.03$. Moreover, given the current discrepancies between experimental measurements of the neutron lifetime ${\tau }_n$, we show that the assumption of a conservative error of $\mathrm{\Delta }{\tau }_n\sim 10\mathrm{s}$ could cause a systematic error of $\mathrm{\Delta }{N}_{\mathrm{eff}}=0.02$. Complementary cosmological constraints on the running of the spectral index and a solution to the neutron lifetime discrepancy are therefore needed for an accurate and reliable future CMB bound of $N_{\mathrm{eff}}$ at the percent level.

We revisit the cosmology of covariant Galileon gravity in view of the most recent cosmological data sets, including weak lensing. As a higher derivative theory, covariant Galileon models do not have a $\mathrm{\Lambda }\mathrm{CDM}$ limit and predict a very different structure formation pattern compared with the standard $\mathrm{\Lambda }\mathrm{CDM}$ scenario. Previous cosmological analyses suggest that this model is marginally disfavored, yet cannot be completely ruled out. In this work we use a more recent and extended combination of data, and we allow for more freedom in the cosmology, by including a massive neutrino sector with three different mass hierarchies. We use the Planck measurements of cosmic microwave background temperature and polarization; baryonic acoustic oscillations measurements by BOSS DR12; local measurements of $H_0$; the joint light-curve analysis supernovae sample; and, for the first time, weak gravitational lensing from the KiDS Collaboration. We find, that in order to provide a reasonable fit, a nonzero neutrino mass is indeed necessary, but we do not report any sizable difference among the three neutrino hierarchies. Finally, the comparison of the Bayesian evidence to the $\mathrm{\Lambda }\mathrm{CDM}$ one shows that in all the cases considered, covariant Galileon models are statistically ruled out by cosmological data.

In this paper we will highlight how a simple vacuum energy dominated inflection-point inflation can match the current data from cosmic microwave background radiation, and predict large primordial tensor to scalar ratio, $r\sim \mathcal{O}({10}^{-3}-{10}^{-2})$, with observable second order gravitational wave background, which can be potentially detectable from future experiments, such as DECi-hertz Interferometer Gravitational wave Observatory (DECIGO), Laser Interferometer Space Antenna (eLISA), cosmic explorer (CE), and big bang observatory (BBO).

The sources of ultrahigh-energy cosmic rays (UHECRs) have been stubbornly elusive. However, the latest report of the Pierre Auger Observatory provides a compelling indication for a possible correlation between the arrival directions of UHECRs and nearby starburst galaxies. We argue that if starbursts are sources of UHECRs, then particle acceleration in the large-scale terminal shock of the superwind that flows from the starburst engine represents the best known concept model in the market. We investigate new constraints on the model and readjust free parameters accordingly. We show that UHECR acceleration above about $10^{11}\mathrm{GeV}$ remains consistent with observation. We also show that the model could accommodate hard source spectra as required by Auger data. We demonstrate how neutrino emission can be used as a discriminator among acceleration models.

We explain the $e^{+}{e}^{-}$ excess observed by the DAMPE Collaboration using a dark matter model based upon the Higgs triplet model and an additional hidden $SU(2{)}_X$ gauge symmetry. Two of the $SU(2{)}_X$ gauge bosons are stable due to a residual discrete symmetry and serve as the dark matter candidate. We search the parameter space for regions that can explain the observed relic abundance, and compute the flux of $e^{+}{e}^{-}$ coming from a nearby dark matter subhalo. With the inclusion of background cosmic rays, we show that the model can render a good fit to the entire energy spectrum covering the AMS-02, Fermi-LAT, CALET and DAMPE data.

As a consequence of axial current conservation, fermions cannot be bound in localized lumps in the massless Nambu–Jona-Lasinio model. In the case of twisted kinks, this manifests itself in a cancellation between the valence fermion density and the fermion density induced in the Dirac sea. To attribute the correct fermion number to these bound states requires an infrared regularization. Recently, this has been achieved by introducing a bare fermion mass, at least in the nonrelativistic regime of small twist angles and fermion numbers. Here, we propose a simpler regularization using a finite box which preserves integrability and can be applied at any twist angle. A consistent and physically plausible assignment of fermion number to all twisted kinks emerges.

The elements (squared) of the neutrino mixing matrix are found to satisfy, as functions of the induced mass, a set of differential equations. They show clearly the dominance of pole terms when the neutrino masses “cross.” Using the known vacuum mixing parameters as initial conditions, it is found that these equations have very good approximate solutions, for all values of the induced mass. The results are applicable to long baseline experiments.

We present an improved analysis of our lattice data for the $\eta –{\eta }^{\prime }$ system, including a correction of the relevant correlation functions for residual topological finite size effects and employing consistent chiral and continuum fits. From this analysis we update our physical results for the masses $M_{\eta }=557(11{)}_{\text{stat}}(03{)}_{\chi \mathrm{PT}}\mathrm{MeV}$ and $M_{\eta }^{\prime }=911(64{)}_{\text{stat}}(03{)}_{\chi \mathrm{PT}}\mathrm{MeV}$, as well as the mixing angle in the quark flavor basis $\varphi =38.8(2.2{)}_{\text{stat}}(2.4{)}_{\chi \mathrm{PT}}^{\circ }$ in excellent agreement with other results from phenomenology. Similarly, we include an analysis for the decay constant parameters, leading to $f_l=125(5{)}_{\text{stat}}(6{)}_{\chi \mathrm{PT}}\mathrm{MeV}$ and $f_s=178(4{)}_{\text{stat}}(1{)}_{\chi \mathrm{PT}}\mathrm{MeV}$. The second error reflects the uncertainty related to the chiral extrapolation. The data used for this study has been generated on gauge ensembles provided by the European Twisted Mass Collaboration with $N_f=2+1+1$ dynamical flavors of Wilson twisted mass fermions. These ensembles cover a range of pion masses from 220 MeV to 500 MeV and three values of the lattice spacing. Combining our data with a prediction from chiral perturbation theory, we give an estimate for the physical $\eta$, ${\eta }^{\prime }\to \gamma \gamma$ decay widths and the singly-virtual $\eta$, ${\eta }^{\prime }\to \gamma {\gamma }^{*}$ transition form factors in the limit of large momentum transfer.